At one point in the past, diesel had a reputation as a dirty, smelly fuel. Today, technology has cleaned up diesel, and in much of the world, including Europe and Asia, diesel is the fuel of choice for automobiles and equipment. Even here in the U.S., diesel-powered equipment can be found in many groundskeeping maintenance facilities thanks to the key benefits it offers, namely, power, torque, durability and fuel efficiency. However, diesel in our country is still viewed as a bit exotic, and uncertainty about maintaining diesel equipment may be one reason for that.

The good news is that maintaining a diesel engine isn’t necessarily more difficult – or even that different – than maintaining a gasoline engine. “In fact, I would say that a basic diesel engine is a lot easier to maintain than a gasoline engine,” says Greg Walker, technical training manager and product support manager with Jacobsen, which uses Kubota engines in its diesel equipment.

For example, he notes, there are a lot fewer things you have to do as far as normal preventive maintenance on a diesel engine: “With diesel, you’re basically just doing fluids, filters and inspections. On a gasoline engine, you’re doing those same things, but there are also a lot more moving parts and wear items and consumable parts that you need to periodically change out – things like spark plugs and wires – and regular tune-ups you have to do.”

“Overall, diesel engines require less maintenance throughout the engine’s life,” states Carl Agee, product marketing manager with John Deere’s Agriculture and Turf Division. “For example, the oil change interval is longer for diesel engines compared to gas engines. Even though diesel maintenance parts tend to be more expensive, because you get a longer service interval diesel still is an advantage.”

One reason gas engines tend to be a little more needy as far as maintenance is that there are more parts involved, says Klasie Baard, sales training manager with Jacobsen. “A diesel engine is compression ignition, so the ignition process is almost spontaneous because of the pressure in the combustion chamber. A gas engine is spark ignition, which means you have to add an ignition system to facilitate the ignition. It’s more complex, and there are more parts,” he explains.


Diesel engines have either glow plugs or air preheater components to heat the air and cylinder to make engine starts easier in cold temperatures. “It is important to note that these components do require inspection, especially when used in the cold season,” cautions John Deere’s Agee. He notes that it’s a frequently overlooked maintenance item.

Whether you’re at a larger sports facility and have a mechanic overseeing equipment maintenance or manage just a single field and have to turn your own wrenches, there are some critical details to pay attention to when it comes to maintaining diesel engines. The first is to read and understand the manual that comes with the equipment. Too often, Walker says, equipment owners and operators lose track of or fail to consult the manuals for their equipment. It’s much easier to properly maintain any piece of equipment when you have the manuals organized and easily accessible.

The biggest problem Walker sees in the maintenance of older diesel engines is a failure to have the fuel injection system tested. “You should have the pressure settings checked and adjusted, and check the spray patterns,” he explains. While the intervals vary depending on the manufacturer, typically these services should be done every 400 hours or once per year as part of an annual service. “On top of that, many owners neglect to do the required valve adjustments and things like that. They’ll do the easy maintenance items, but they won’t do the more difficult things,” Walker observes.

Failure to perform these maintenance items as recommended can result in a loss of power in the engine, which results in a loss of power to all the systems, including the drivetrain and mower functions, as well as overheating. It might also jeopardize the warranty.

Many newer diesel engines include a fuel/water separator. Some machines have a light that illuminates to indicate the separator needs draining; in other cases, this item should be checked daily.

“If you have a failure of that magnitude, the first thing that all manufacturers are going to ask you for is your maintenance records,” says Walker. Frequently, the result is that the operator has no maintenance records at all, or a sheet of paper with scribbled notes on it. He recommends creating a good record-keeping system that shows when all maintenance, from filter changes to valve adjustments, were completed. “Having good records will also show you your cost of ownership, which will help tell you when a particular piece of equipment is becoming more expensive to maintain than it would be to buy a newer model,” he adds.

While ethanol has been getting a lot of attention for the problems it can cause in gasoline engines, including possibly increasing maintenance and decreasing service intervals, there are also some key things to remember when it comes to diesel fuel.

“Diesel engines do not like fuel that’s been stored for a long time,” emphasizes Walker. “You will get water into the system, which creates algae. The algae grows and it will clog up your fuel systems.” While there are various additives on the market that claim to help fight this problem, the best bet is to set up a fuel-buying program that prevents diesel sitting around for extended periods, either in cans or in equipment, he advises. “If winter is coming and you’re getting ready to mow for the last time of the year, you don’t want to fill that tank to the top and then use only 1 gallon out mowing and let the rest sit for six months in the tank. That’s just not a good practice,” says Walker. “You want to make sure you’re always using your fuel up, and then putting in fresh fuel.”

Some diesel engines include a “filter minder” that turns red to indicate that the air filter should be changed immediately. On units with this feature, it’s best to watch the indicator rather than removing and checking the air filter regularly, which can allow dust and debris into the system.

When the equipment is being used regularly, Agee advises keeping the tank topped off. “Keep all storage tanks as full as practicable to minimize condensation,” he explains. “Doing so will prevent condensation from building up that can cause issues down the road. By checking the equipment regularly and keeping up the suggested maintenance, operators can experience a long life expectancy from diesel engines.”

To further help prevent problems, newer diesel engines typically include a fuel/water separator, as well as a filter before and after the fuel pump, notes Walker. These are easy-to-monitor and maintain. He says, “With the newer engines, you just have to drain the water out of the filter occasionally. Some of the better systems will actually have a light or some other indicator to tell you it’s time to do that.”

This is just one example of the features in many newer diesel engines that someone with experience maintaining diesel equipment in the past may not be familiar with, states Walker. “For example, some will have a filter inside the fuel pump, so you need to open up the bottom of the fuel pump and get that filter out. In fact, the newer systems use multiple filters, because with the new Tier IV restrictions there’s a lot more damage that can occur from even minute particles in the fuel system,” he explains. “So there are more filters you have to change and maintain and keep an eye on at the recommended times. If you don’t know where all your filters are, they can cause you problems.”

Still, Walker says, “you don’t need to be afraid” to work on the newer high-tech Tier IV-compliant engines. “In a sense they’re easier to maintain, because they actually give you more information,” he notes.

Walker points out one area where diesel equipment owners tend to do too much maintenance: changing the air filter. A lot of the newer diesel engines have a “filter minder” function that lets the operator quickly see if the filter needs to be changed. “There’s a pressure switch that will turn red if there’s back pressure in the system, and that tells you that your filter is clogged,” he explains. Many people are in the habit of frequently taking the filter out, checking it visually for dirt, banging and tapping debris off it, and then putting the filter back in. However, removing and replacing the filter too frequently increases the chances that contaminants will get into the system, he says. It’s better to leave the filter alone until the built-in system says maintenance is required.

When you need to replace a filter, or any other part on your diesel machine, Jacobsen’s Baard recommends using only parts recommended by the manufacturer. “If you buy some other type of filter, you have no guarantee that it will give you the protection you need for the investment you’ve made in the equipment,” he explains. Today’s engines operate at very fine tolerances, so whether it’s a filter to keep out contaminants, the coolant, the engine oil or any other part, manufacturers test, work with component suppliers and recommend specific products for a reason, Baard states. Trying to save a few dollars on a part might jeopardize a unit that costs tens of thousands of dollars. Once again, a warranty could be voided if the manufacturer’s recommendations weren’t followed.

Just as it’s important to use the right parts and fluids when maintaining diesel engines, so is using the right type of fuel.

“For operators who are using equipment that meets Final Tier IV requirements, it is pertinent to pay attention to the type of fuel used,” states John Deere’s Agee. “It is critical to use an ultra-low sulfur fuel in Final Tier IV engines. Using fuel with high sulfur content will create issues with some of the components of the engine, leading to added costs in the future.”

A diesel-powered John Deere 1550 TerrainCut front mower.

Higher up-front purchase costs and unfamiliarity with maintenance procedures may keep some sports turf managers from making the move to diesel equipment, but Agee says looking at the big picture, including costs over the life of the equipment, makes diesel an appealing choice. “The life expectancy of the diesel engine will offset the initial costs over time,” he says. “It is also important to weigh the cost of maintenance over the life of the engine, which is less when compared to gasoline engines, which require shorter service intervals.”